Powder cosmetics such as powder foundation can be obtained by molding the powder, wherein an oil component as a binder, surfactant, etc. are added to and mixed with the main powder component. Normally, powder applicators such as a puff, a sponge, and a brush are used for application. The conventional general powder cosmetics have been produced by homogenizing with a hammer mill such as a pulverizer after the powder component and the oil component are mixed with the use of agitation mixers such as a Henschel mixer, Nauta mixer, ribbon blender, and kneader, and by press-molding into a metal or plastic inner tray. Such a conventional method is called a dry process because the powder component and the oil component are mixed without the addition of a solvent.
However, fully satisfactory powder cosmetics have not been obtained, by the above-described conventional dry process, in terms of the practical characteristics such as extensibility on the skin, adhesion, feeling of particulate fineness, and long-lasting property, and in terms of the impact resistance. The cause of this is that the homogenization of the powder component and the oil component is not satisfactory; thus the agglomerated powder component remained, and the oil component may be unevenly distributed in the agglomerated powder.
On the other hand, various production methods or molding methods have been developed, in recent years, to improve the practical characteristics of powder cosmetics. For example, the following wet processes have been proposed: the filling-solidifying method of cosmetics, wherein a solvent such as alcohol is added to a cosmetic base to make a slurry, the slurry is filled in a container, and then the solvent is removed by vacuum suction (refer to patent literature 1); the production method of compact powder makeup cosmetics, wherein the base material containing a specific powder, as a powder component, and oil is added to a solvent to make a slurry, and then the solvent is removed (refer to patent literature 2); and the production method of powdery solid cosmetics, wherein a slurry obtained by mixing, in a solvent, the powder component and the oil component as a binder, is treated with a media agitating mill to uniformly coat the surface of the powder component with the oil component, the solvent is removed, and the press molding is carried out to obtain powdery solid cosmetics (refer to patent literature 3).
However, even by the above-described production methods or molding methods, the practical characteristics such as the feeling of particulate fineness and long-lasting property, and the impact resistance were not satisfactory. Especially, in the wet process, the oil component is uniformly coated over the entire surface of powder. Thus, there has been an issue in that the oil absorptiveness of the powder component decreases drastically, and the long-lasting property against the oil such as sebum is poor. In addition, the solvent removal/drying processes are separately necessary in the above-described wet process. Therefore, not only the process becomes complicated but also there are safety issues and environmental issues.
In order to improve the long-lasting property of powder cosmetics, a powder component whose surface is treated with a fluorine compound having water-repellent and oil-repellent properties has been used. However, the homogenization of the powder component and the oil component was difficult because of the oil-repellent property of the fluorine compound. Thus, the powder agglomeration was easily caused; and the expected improvement effect of long-lasting property could not be achieved. In addition, the feeling in use deteriorated sometimes. In order to provide an excellent texture in use, such as extensibility, spherical elastic powder of silicone, polyurethane, etc. has also been blended. However, there has been an issue in that the impact resistance, in particular, becomes worse because of a difficulty in the homogenization of the powder component and the oil component. Furthermore, in order to improve the adhesion to the skin, long-lasting property, etc., the use of high-viscosity oils has been tried. However, it is very difficult to uniformly disperse high-viscosity oil into the powder by the conventional method. In addition, there has been an issue in that detrimental effects, such as the promoted agglomeration of the powder component, are caused.
Patent Literature 1: Japanese Examined Patent Application Publication No. S61-54766
Patent Literature 2: Japanese Unexamined Patent Publication No. H7-277924
Patent Literature 3: Japanese Patent No. 3608778